Field of the Invention
The present invention relates generally to an introducer for expanding an opening into the body for a medical procedure.
Description of the Related Art
Introducer sheaths are used in a variety of interventional procedures for access into a patient's artery for the purposes of providing a lumen for the passage of other interventional devices such as balloon catheters, stents, guide catheters, temporary heart pumps, artificial heart valves and guide wires. Introducer sheaths typically comprise a tubular element with a hub at the proximal end (the end proximal to the doctor or other medical professional) and a dilator inserted within the tubular element. The hub typically has a valve at the proximal end to prevent blood loss through the lumen during insertion of devices through the valve and the main lumen of the introducer. The hub also incorporates a port and a tube terminating in a stop cock. A syringe containing saline (for example) may be connected to the stopcock to flush any air out of the annular space between the dilator and the introducer shaft prior to insertion of the introducer within a patient's vessel. A Luer connector at the proximal end of the dilator may also be used for flushing air out of the inner lumen of the dilator prior to using the introducer. The dilator can be inserted into the lumen of the introducer prior to insertion into a patient's vessel. The dilator is tapered at the distal end (the end distal to the doctor or other medical professional) and has a central lumen for tracking over a guide wire. The dilator serves to provide a transition between the guide wire and the introducer internal diameter during advancement of the introducer into a patient's vessel.
Introducers come in a variety of different sizes depending on the procedure being performed. For example, a coronary stenting procedure may utilize a size 5 F or 6 F introducer sheath. The sizes 5 F or 6 F refer to French catheter sizes (also referred to as Fr sizes), wherein a round catheter of size 1 French (1 F or 1 Fr) has an external diameter of ⅓ mm. A size 6 F catheter has an external diameter of 2 mm. The introducer sheath/dilator may be inserted into a patient vessel over a pre-positioned 0.035″ (0.035 inch) guide wire. The dilator resides within the inner lumen of the introducer during access into the patient's vessel. After the introducer is in position, the guide wire and the dilator may be removed, leaving the introducer in situ. A valve at the proximal end of the introducer prevents blood loss from the patient through the introducer while also allowing devices to be inserted through this valve. During a coronary angioplasty procedure, for example, a size 5 F or 6 F guide catheter may be advanced through the main lumen of the introducer and advanced through the patient's vasculature. The tip of the guide catheter may be positioned in the ostium of the vessel being treated. Balloons and stent delivery systems may then be advanced through the guide catheter lumen.
In more recent years, larger diameter introducers are being used for specific procedures that require a delivery system with a large profile. During aortic valve replacement, for example, the delivery system profile may be as large as size 18 F-22 F. This larger delivery system profile requires an introducer sheath with an inner diameter of size 19 F-24 F, for example. In such instances the introducer outer diameter may be size 24 F (8 mm). These introducers are typically inserted into the femoral artery. For some patients their femoral artery may be less than 8 mm diameter so that it would not be possible to treat certain patients with specific delivery systems that have a profile or outside diameter that is too large for the blood vessels of the particular patient. To address this shortcoming, some companies have developed expandable-type introducer sheaths that have a specific profile during delivery into the patient's vasculature and are capable of a certain amount of expansion during advancement of the large profile delivery system through the introducer inner lumen. These commercially available introducers have several drawbacks.
One commercially available expandable introducer comprises a sheath with a longitudinal slit along its length. The sheath is then folded inside itself so that its profile, or external diameter, is significantly lower, or less, than the original profile. A very thin layer of material connects both sides of the longitudinal slit. Upon advancing of the delivery system through this introducer the sheath unfolds but when it does so it leaves an edge protruding along the length of the sheath. The edge presents a risk of vessel trauma or injury during the remainder of the procedure and when the introducer is being removed from the patient. In addition the forces required to advance the delivery system through this introducer can be as high as 25 Newton's. This represents a potential risk for patient injury.
Another commercially available introducer comprises a braided-type shaft that is folded down into a reduced profile configuration and a balloon catheter residing within the internal lumen of the introducer. When the introducer is advanced in position the balloon can be inflated to expand the introducer profile within the vessel. The balloon catheter can then be removed and the delivery system can then be passed through the introducer. The introducer profile does not revert to its original lower profile after the delivery system has been passed through the introducer so that this introducer only provides for a lower profile (smaller external diameter) initially during insertion into the patient vessel. In addition, the balloon catheter within the introducer requires additional steps that must be completed when using this introducer such as purging the balloon catheter, inflating the balloon catheter and removal of the balloon catheter. The balloon catheter must remain inflated for one minute during expansion of the introducer. This is a time related disadvantage with this introducer.
It is therefore desirable to have an expandable introducer sheath that is capable of atraumatic expansion and that provides for lower insertion forces for devices being inserted through the expandable introducer sheath.